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TP12B Ecological Effects of Cholinesterase Inhibitors
() Indirect effects of an insecticide on Rana sphenocephala (southern leopard frog) tadpoles.
Mills, N1, Semlitsch, R2, Bridges, C3, 1 Harding University, Searcy, AR, USA2 University of Missouri--Columbia, Columbia, MO, USA3 USGS Columbia Environmental Research Center, Columbia, MO, USA
ABSTRACT- Pesticides can alter the life-history traits of a species, and thus presumably influence that species' population dynamics, by causing changes in community structure (i.e., indirect effects). Because competition and predation are important components of a community that can act to regulate a population, it is important to understand how they interact with pesticides. Our microcosm study investigated how the insecticide, carbaryl, interacted with predation and competition to influence Rana sphenocephala life-history traits. Our study clearly demonstrated that a pesticide can cause changes in competition and predation intensity in the aquatic community which in turn alters Rana sphenocephala life-history traits. Carbaryl generally increased the survival of Rana sphenocephala tadpoles. However, the increase in survival was greatest in microcosms containing predators, largely due to pesticide-induced mortality of the predators. Carbaryl also exacerbated the effects of competition by decreasing periphyton abundance. This increase in competition resulted in slowed tadpole growth rates and ultimately smaller metamorphs. Thus, we conclude that investigations of the effects of pesticides on a species of interest should go beyond standard toxicological protocols and examine the effects of the pesticide within the context of the community of which the species is normally a part, placing special emphasis on understanding the mechanisms mediating any observed indirect effects.
Key words: carbaryl, competition, Rana sphenocephala, predation
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